1. Field of the Invention:
The present invention relates to brushes for cleaning underwater surfaces and particularly to hydrodynamic flow vanes for increasing contact pressure against a surface being cleaned by motion of an abrasive cleaning device.
2. Relation to the Prior Art:
In brushing the sides of a swimming pool, it is awkward and difficult to maintain any kind of forceful contact by the brush against the sides of the pool. This has led to a number of innovative devices to utilize the dynamics of liquid flow to provide the desired contact pressure. The flow vane of Otto, U.S. Pat. No. 2,243,576 was a simple rectangular plate pivotally mounted at the ends of the brush. The spacing between the plate and the back of the brush limited the pivotal movement of the vane so that it provided equal pressure to the brush on both up and down strokes.
Shouldice in U.S. Pat. No. 3,003,166 describes a similar but more complex vane having a more balanced structure with blades extending both ways from the pivotal axis. The blade nearer the brush is captured in a housing and its movement is limited by the housing lips. Again the limits are the same for both directions of motion.
Gibellina in U.S. Pat. No. 3,402,413, discloses a nonpivotal vane that is shaped to produce greater contact pressure on a forward stroke than on a reverse stroke.
Feinberg in U.S. Pat. No. 4,637,087 provides a fixed vane with a plurality of apertures blocked by check valves so as to reduce the contact pressure on the return stroke.
Both of the latter two patents recognized the value of reducing flow impedance on the return stroke. Both also provided devices that were adaptable to after market use. They are readily attachable to preexisting brushes.
The present invention returns to the pivotal simplicity of the Otto patent with a device that has lower return stroke impedance than any of the references and is well adapted to after market use.